body {
    font-family: Arial, sans-serif;
    text-align: center;
}

.hidden {
    display: none;
}

.theme-btn {
    min-width: 130px;
    font-size: 1rem;
    transition: all 0.15s ease;
}

.theme-btn.selected {
    box-shadow: 0 0 0 3px #fff;
}